Spoiler to about episode 22. Watch this, there's no reason it won't be worth it. Honestly, I'm saddened this wasn't in the series itself. This small bit was not necessary, and such I understand, but it really helps to characterize Ketil, but also to show how the Norse were so opposed to running away, in contrast to when they really did run away. The plurality of human, which is strong in the series. Of course, it's about the secondary characters, but that doesn't mean it's less important. Just look at Canute's scene in the first season. So, in terms of meaning, it meshes with the series (asit should). Nothing exactly new, but if you read my review, you could have already watched the episode, so go do that.
No comments on music, art or enjoyment, they're the same as the normal series. I don't think a dubbed version of this is available.